The Substitution control is used on ASP.NET web pages that are configured to be cached. The Substitution control allows you to create areas on the page that can be updated dynamically and then integrated into the cached page. For details on using the Substitution control, see Dynamically Updating Portions of a Cached Page in the MSDN library.
To add a Substitution control to a page
Drag the Substitution control from the Toolbox panel to your page.
Set properties for the control in the Tag Properties panel.
For a full description of all Substitution control properties, see Substitution Properties in the MSDN library.